Sorting in Java
This article will illustrate how to apply sorting to Array, List, Set and Map in Java 7 and Java 8. Let’s start by sorting integer arrays first using Arrays.sort() method. We’ll define the following int arrays in a @Before jUnit method:
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Continuing our illustration of using arrays, we look at a simple technique for sorting the random numbers in the array into ascending order. In reality, there are better ways of sorting, but the one we're going to use here has the redeeming feature of being easy to understand and only need a few lines of Java.
Sorting is ordering a list of objects. We can distinguish two types of sorting. If the number of objects is small enough to fits into the main memory, sorting is called internal sorting. If the number of objects is so large that some of them reside on external storage during the sort, it is called external sorting. In this chapter we consider the following internal sorting algorithms
Sorting Lists in Java is a common task. For this Java provides Comparators and Comparables. These are Interfaces which are required to be implemented for sorting purpose. For the demonstration we will consider one at a time. sort method of Collections class in used to sort. This method is overloaded one takes List as its parameter and other takes List and Comparator as its arguments.
JDK enhancement proposal 103 brings a new way of array sorting which uses the Fork/Join parallelism technique to provide sorting of arrays in parallel. This new feature is going to be added in our forthcoming Java 9 release. Currently, we have two sorting implementations, one sorts arrays and another sorts collections. These two implementations perform sort in a single thread.
Below is the java source code on sorting numbers using bubble sort . You can decide on how to sort a number either ascending or descending by just changing the comparison operator in the method BubbleSort.There are many sorting algorithms on sorting numbers but the most used is the selection sort. Actually, bubble sort is not a better choice on sorting numbers but it is pretty good to program while learning different sorting algorithms as well as recursion. It exposed the programmers on different ways on how to solve and program a certain problem and widen his/her knowledge as well as be able to compare its usefulness. After this program I will also upload the selection sort.
Bubble Sort is the first sorting algorithm I learned during my college day, and after so many years it's the one I remember by heart. It's kind of weird that one of the most popular sorting algorithm is also one of the worst performing sorting algorithm. Bubble sort's average case performance is in O(n^2), which means as the size array grows, the time it take to sort that array increases quadratic. Due to this reason, bubble sort is not used in production code, instead quick sort and merge sort are preferred over it. In fact, Java's own Arrays.sort() method, which is the easiest way to sort an array in Java also uses two pivot quicksort to sort primitive array and stable mergesort algorithm to sort object arrays.
Sorting is one the first algorithm that we learn in computer science. Sorting is such an interesting area that it has around 20+ algorithm and it is always difficult to decided which one is best. Sorting algorithm efficiency is measured in terms of time taken & space required. Some time bubble sort is best because it has no space requirement and for device where space is constraint or random access of element is not possible then it can be good fit .
In this tutorial, it shows the use of java.lang.Comparable and java.util.Comparator to sort a Java object based on its property value.
Here is a small but very useful tip that every Java programmer should be aware of. Have you ever tried sorting arrays in Java? Well, java.util.Arrays class has built in method to make your job easy. You can use following method to sort any array in Java.
Have you ever wondered how to sort elements in a List? Java's collections classes and interfaces (in the java.util package) provide the ability to sort arbitrary datasets. In this article, we look at how to sort elements stored in Lists, how to provide sorting orders for data classes, and how to use a generic mechanism for sorting JavaBeans.